1. Field of the Invention
The present invention relates to a filler cap for a fuel tank to seal a filler opening arranged to an automobile and so on. In more detail, the present invention relates to a filler cap for a fuel tank attached to a filler opening of a fuel tank and arranged with an air passage channel to connect between inside and outside the fuel tank in a cap main body composed of an outer cap and an inner cap and with a valve mechanism portion in this air passage channel.
2. Description of the Related Art
In the past, in a filler cap for a fuel tank of an internal-combustion engine arranged to an automobile and so on (such as an automobile, an agricultural machinery, a power generator, a lawn mower, a motor cycle, a boat and a ship, a construction machine, and a roadwork machine), there has been arranged an air passage channel to inhale an atmospheric air because it is necessary to inhale an atmospheric air the amount of which is in proportion to the volume of a fuel consumed in the fuel tank.
Accordingly, a vaporized gas generated from the fuel in the fuel tank is discharged into an atmosphere through the air passage channel arranged to the filler cap, thereby causing a problem of an environmental pollution. In addition, if the fuel tank arranged to an automobile and so on is tilted more than a prescribed angle, there has been a risk that the fuel leaks out through the air passage channel so that the fuel may catch fire.
In view of the foregoing, the applicant proposed a practical filler cap for a fuel tank capable of preventing the fuel from leaking out through the air passage channel in the filler cap even when the fuel tank is tilted to a prescribed angle, and at the same time, capable of preventing environmental pollution and improving fuel consumption without discharging a harmful gas evaporated from the fuel to the outside, and consequently, the structure of the filler cap can be made simple and thus can be produced cheaply (see Patent Literatures 1 and 2).
That is, the applicant proposed a filler cap wherein
a valve body is put on a cylinder main body such that, in the state in which its peripheral edge part is in contact with a first wall surface slanted upward to connect a second wall surface and a third wall surface of the cylinder main body so as to shut down communication between a second space and a third space;
when the pressure inside the fuel tank is increased above a pressure for a deformation strength prescribed to the valve body, a central part of the valve body moves upward and enters into the third space thereby causing deformation so as to shorten the outer diameter of the valve body to form wrinkles and as a result, in a peripheral part of the valve body are formed a portion contacting to a lower end of the third wall surface to form the third space of the cylinder main body and a concave portion not contacting thereto, and consequently, the second space and the third space are connected via a space of this concave portion to release an excessive pressure to outside the fuel tank thereby bringing the pressure inside the fuel tank to lower than the pressure for the deformation strength, and
when the pressure inside the fuel tank becomes negative by consumption of the fuel inside the fuel tank, the peripheral part of the valve body is sucked toward the fuel tank by this negative pressure whereby the peripheral part of the valve body hangs down by using a peripheral edge part on the upper plane of the small diameter portion of the valve-body-supporting member as a pivot thereby forming a gap between the slanted first wall surface of the cylinder main body and the valve body so as to connect between the second space and the third space thereby introducing an atmospheric air into the fuel tank so as to bring the state of an atmospheric pressure;
whereby functioning as a safety valve as well as a one-way valve.